Although this is a convenient way to think of the term, it's not accurate.
Instead, the word relational has its roots in the terminology that Codd used to define the relational model.
This article was adapted by the author from the design chapter of , Sybex 1994, by Ken Getz, Paul Litwin and Greg Reddick, and is reproduced here with permission.
Don't let the fact that the examples were done for Access 2 fool you.
This article is by no means comprehensive and certainly not definitive.